1. Field of the Invention
The invention relates to a hydrogen gas supply unit and, more particularly, to an art of removing an odorant from a mixed gas containing hydrogen gas and the odorant.
2. Description of the Related Art
A fuel cell system includes a fuel cell, a fuel gas supply portion, and an oxidative gas supply portion. The fuel cell generates electricity by means of hydrogen gas contained in a fuel gas supplied from the fuel gas supply portion and oxygen gas contained in an oxidative gas (air) supplied from the oxidative gas supply portion.
In the fuel cell system, a mixed gas containing hydrogen gas and an odorant is utilized for the purpose of detecting leakage of hydrogen gas at an early stage. In many cases, however, the odorant deteriorates output characteristics of the fuel cell. Therefore, the fuel gas supply portion is generally provided with an odorant removal portion for removing the odorant from the mixed gas by adsorbing the odorant. A fuel cell system as mentioned herein is disclosed, for example, in Japanese Patent Application Laid-Open No. 2002-29701.
There is a limit to the amount of the odorant that can be adsorbed by the odorant removal portion. The speed at which the odorant removal portion adsorbs the odorant decreases as the amount of the adsorbed odorant increases. Thus, if the amount of the odorant increases, the odorant removal portion deteriorates in adsorption capacity (e.g., adsorption speed). In the fuel cell system of the related art, therefore, the odorant removal portion needs to be replaced with another one. This problem develops not only in a fuel cell system but also in a hydrogen gas supply unit for supplying a predetermined apparatus with hydrogen gas by removing an odorant from a mixed gas containing hydrogen gas and the odorant.